Centrifugal blasting machine



Dec. l, 1942. c. E. UNGER CENTRIFUGAL BLASTING MACHINE.

Filed July l2, 1940 2 Seet-S-Sheet l INVENTOR flmser E @er All ATTORNEYDec. 1, 1942. c. E. UNSER v-'-"23302041 GENTRIFUGAL BLASTING `MACHINEWFiled .my 12. i940v 2 sheefcs-sneet 2 Ws *"a ATTORNEY Patented Dec. l,1942 CENTRIFU GAL BLASTIN G MACHINE Chester E. Unger, Mishawaka, nd.,.assignor to The American Foundry Equipment Company, Mishawaka, Ind., acorporation of Dela- Ware Application July 12,1940, serial No. 345,035

' 15 claims. (01.51-9) This invention relates to centrifugal blastingmachines, and more particularly to that type of blasting machine whichcomprises a bladed rotor having means positioned centrally thereof fordirecting the abrasive into the path of rotation of the blades of therotor whereby the abrasive thrown by the blades may be directed in aconiined or concentrated stream against the article undergoing vtreatment positioned at one side thereof.

In accordance with this invention, the centrifugal blasting machineembodies a bladed rotor which may comprise a pair of spaced side Walldiscs rigidly connected together and fixed to the end of a high speedshaft. Abrasive throwing blades are positioned between and supported bythe side wall discs and are arranged in spaced generally radiallyextending relationship with the inner ends of the blades extending shortof the axis of rotation of the rotor to provide a central space therein.

An important feature of this invention comprises the provision of atubular impeller positioned within the central space of the bladed rotorand fixed to rotate therewith, which is so designed as to effectsubstantially even distribution of the abrasive over the full width ofthe advancing face of the blades. The abrasive is fed into the tubularimpeller by a suitable stationary feed spout which discharges theabrasive onto the inside surface of the tubular impeller. The tubularside wall of the impeller is provided with a plurality of dischargeports or slots whose side edges are positioned between the side flangesof the channel shaped blades. tent of each slot is relatively short sothat the slot is relatively narrow in axial extent. The number of slotsemployed are preferably equal in number to the abrasive throwing bladesand each slot is preferably positioned slightly in advance of itscorresponding blade. The abrasive deposited on the interior surface ofthe tubular side wall of the impeller is held in hugging relationship tothe inside surface by centrifugal force. Agitating lugs fixed to theinside surface of the impeller may in some cases be provided to assistin bringing the abrasive deposited therein up-to peripheral speed. Theselugs also serve to assist the distribution of the abrasive between thenarrow discharge ports so that substantially uniform discharge of theabrasive through the full axial width of the discharge ports iseffected. Y.

When the bladed rotor is rotated at blasting 'Ihe peripheral ex- Aspeeds the blades thereof exert a fan action which Mi normally produceshigh velocity air movements within the central space of the wheel.

A baille plate or deflector segment is positioneds within the tubularimpeller and serves to baiile the air currents generated by the rapidlyrotating blades within the central space of the rotor, so that the portsof the tubular impeller when rotating through 'an area which isgenerally opposite the arcuate side wall and the heel of the deilectingsegment, appear to experience a high velocity inow of air through theports, which prevents any substantial quantity of abrasive escapingoutwardly through the ports as they rotate through this area. This area,through which the air flows at high velocity through the ports of thetubular impeller inwardly into the same, might be referred to as apressure area. velocity air currents escape from the interior of therotating tubular impeller through the ports thereof when they move overa relatively short peripheral area which is adjacent but,slightly inadvance of the tip end of the deiiector segment, which area might betermed a suction area. The outflowing air at the suction area obviouslydoes not obstruct but facilitates the discharge of abrasive through thedischarge ports of the impeller as they move through the suction area.The inside surface of the arcuate side wall of the deflector segmentalso serves to guide any abrasive thrown thereagainst along the insidesurface until it is free to discharge from the tip end of the deflectorsegment. 'Ihe narrow discharge ports in the tubular impeller which -havean axial width approximating that of the throwing surface of the bladesperform the highly important function of effecting substantially uniformdistribution of the abrasive directed onto the inner ends of theadvancing blades through substantially the full abrasive throwing widththereof. y

Another feature of this invention is the provision of a spiralling ribor iange xed to the outer periphery of the end portion of the feed spoutwhich extends into the tubular impeller. This spiralling rib furtherfacilitates the distribution of the abrasive within the tubular impellerso that the abrasive will discharge substantially uniformly throughthefull axial width of the narrow discharge ports thereof. This spirallingsive within the tubular impeller so that the abrasive is moreeffectively brought under the inuence of the controlled and deflectedair currents The `highgenerated by the bladed rotor within the tubularimpeller.

Various other features `and advantages oi the invention will be apparentfrom the following particular description and from an inspection of theaccompanying drawings.

Although the novel features which are believed to be characteristic ofthis invention will be particularly pointed out in the claims appendedhereto,.the invention itself, as to its objects and advantages, and themanner in which it may be carried out, may be better understood byreferring to the following description taken in connection with theaccompanying drawings forming a part thereof, in which:

Fig. 1 is across-sectional view of a centrifugal blasting machine havingthe abrasive deflecting device positioned within the tubular impeller,this view showing the machine as it appears when looking in thedirection of the arrows along line I-I of Fig. 2;

Fig. 2 is a cross-sectional view of this machine as it appears whenlooking in the direction of the arrows along the line 2-2 of Fig. 1;

Fig. 3 is a perspective view, partly in section, of the abrasiveimpeller device associated with this machine; 't

Fig. 4 is a perspective View of a normally stationary deflector employedto effect directional control of the abrasive from the bladed rotor ofthe machine shown in Figs. 1 and 2;

Fig. 5 is a cross-sectional view of a centrifugal blasting machinehaving modified means for feeding and controlling the direction ofabrasive discharged from the bladed rotor, this View being taken alongline 5-5 of Fig. 6;

Fig. 6 isa cross-sectional view of this centrifugal blasting machine asit appears when looking in the direction of the arrows along line 6--6of Fig. 5; and

Fig. '7 is a perspective view of the abrasive deiiecting device employedto effect directional control of the abrasive fired by the bladed rotorforming a part of the machine shown in Figs. 5 and 6.

Similar reference characters refer to similar parts throughout theseveral views of the drawings and the specification.

The centrifugal blasting machines which have been shown in the drawingsto illustrate embodiments of this invention, generally comprise a bladedrotor I mounted on the end of a high speed shaft which has associatedtherewith a device or devices for giving to the abrasive suppliedthereto through a suitable feed spout an initial velocity in the generaldirection of rotation of the blades of the rotor and a device or devicesdisposed generally centrally of the bladed rotorA for controlling thedirection of discharge of the abrasive fired by the rapidly rotatingblades of the rotor. l

Generally speaking, the bladed rotor, constructed of suitable metal, maycomprise a pair of spaced side wall forming discs 2 and 3 which are heldin xed spaced relationship by means of suitable studs or spacers 4 whichare welded or otherwise rigidly fixed` to the side wall discs 2 and 3.The bladed rotor is mounted upon a sturdy shaft 5 which rotates withinsuitable spaced bearings, the shaft being suitably connected to asuitable power source so as to be rotated at high speed. A hub 6 isfixed to the end of the shaft 5 as by means of a suitable spline 1 andthe hub flange is suitably secured as by bolts 8 to the adjacent sidewall disc 2. vThe front side the side wall discs 3 and 2 respectively.As thus constructed, the inner ends of the blades b and circular opening'of substantially the same diameter defined by an inner circular edge9'.

A plurality of throwing blades b,`general1y formed of wear resistantmetal, are radially arranged in spaced relationship between the metalside wall discs 2 and 3. Four to eight such blades b are generallyprovided. 'I'hese blades are preferably channel shaped in cross-section,definingan abrasive receiving bottom wall III and a pair of side flangesII t'o retain the abrasive within the confines of the advancing face ofthe bottom wall I0. Each blade is inserted into paired slots or groovesformed in the side wall discs 2 and 3, which grooves support the bladesin radial spaced arrangement. The

inner ends I2 of the blades are generally in approximate alignment withthe peripheral edges 3 and 9' which define the central openings in thecircular openings in the side wall discs 2 and 3 define a central spaceI5 within the bladed rotor within which .the abrasive impelling andcontrolling devices may be positioned. 'I'he blades b are removed whenworn and fresh blades inserted through the periphery of the rotor, andmay be held in operative position by set screws I3 threaded into theside wall plates 2 and 3, the inner ends of these set screws extendinginto suitable recesses I4 in the side edges of the blades. Bymanipulating the set screws I3 the blades b can beeasily withdrawnthrough the periphery of the rotor.

Referring more particularly to the abrasive blasting machine illustratedin Figs. 1 to 4 inclusive, a generally cylindrical impeller device 20,cast from wear resistant metal, is positioned within the central spaceof the rotor. This impeller device, shown separately in Fig. 3,comprises a cylindrical wall 2| which is closed at the inner end by endwall 22. This end wall may be designed to seat against the inside faceof the hub 6 and may be fixed to rotate with the bladed rotor by meansof a bolt 21 which extends through the end wall 22 of the impellerdevice and is threaded into a threaded opening in the end of the driveshaft 5. The front end of the impeller device 20 may be provided with anintumed fiange 23 which defines a circular opening 24 into which thedischarge end of the abrasive supply spout 40 may be inserted. -Thetubular wall 2I of the impeller device may be provided with a pluralityof spaced discharge openings 25 preferably equal in number to the numberof blades b of the rotor. The outer periphery of the tubular side wall2| of the impeller extends closely adjacent the inner ends I2 of theblades b.

The tubular impeller device is preferably so positioned that eachdischarge opening 25 is positioned slightly in advance of thecorresponding blade b of the rotor so that the abrasive will dischargefrom the opening 25 with the least interference with the inner ends I2of the blades b. The tubular impeller device is alsoso positioned thatthe side edges of the opening 25 extend generally between the sideflanges I I of the blades b. The openings 25 are preferably relativelynarrow or short in their peripheral extent so that in this machinesubstantially unlform quantities of abrasive will discharge through eachopening. The inside surface 2l of the tubular impeller device provides acircular rotating shelf upon which the abrasive is deposited as itdischarges from the discharge end 4| of the abrasive supply spout 4|.l.lThe abrasive a deposited on the shelf 28 dened between the end wall 22and the adjacent side edges of the openings 25 rotates with this shelfand collects thereon in a ring-shaped pile until its angle of repose isovercome, when it drops out through the narrow openings 25. To bring theabrasive up to a speed approaching the peripheral speed of the shelf 28,a plurality of radially extending agitating lugs 28 are preferablysecured to the inside face of the end wall 22.

In order that a central space may be provided within the bladed rotordeep enough to receive the tubular impeller and provide an adequateabrasive supporting shelf 28, the hub 6 may be provided with an internalcircular recess. Such a circular recess may be made by providing as apart of the hub a circular plate 43 having a circular opening 44 on theinside face thereof, which is secured to the side wall disc 2 of therotor by the bolts 8. It will be appreciated that, if desired, the plateportion 43 may be formed as an integral part of the hub.

apertures 53 through which securing bolts 63 extending through spacedapertures 63 in the bottom wall 6| of the dish-shaped member 58 extend.The spaced h'oles or slots,63 in the bottom wall 8| may be arranged in acircle s o that the securing screws 63 may be selectively insertedthrough these openings or slots to attach the control cage segment inany desired operative position.

Abrasive supplied to the feed spout 48 discharges from the inner end 4|thereof into the tubular impeller 28 where it collects upon the insidesurface of the tubular wall 2| thereof. The control cage segment 58serves to baille the high velocity air currents so that during highspeed rotation of the bladed rotor air is drawn through the ports duringa predetermined clockdial position during rotation thereof, .so as toprevent escape of any substantial quantity of abrasive at this point.The segment 50 operates to force the air out through the ports 25 duringthe remaining predetermined clockdial position during rotation so as topermit escape of abrasive at this area.

The abrasive supply spout 40 is supported upon a suitable bracket 42fixed to a suitable stationary mounting. The abrasive a supplied to thefeed spout 40 discharges from the inner end 4| thereof and drops uponthe shelf 28 of the tubular impeller. The abrasive dropped on the shelf28 quickly assumes the speed of rotation of the shelf, assistedby theagitating lugs 26, and collects on this shelf until the angle of reposeof the pile of abrasive deposited thereon is overcome.

Directional control of the thrown abrasive is effected by the provisionof an arcuate baille plate or segment which is positioned within thetubular impeller in the manner illustrated in Figs. 1 and 2.

The control cage segment 50 may be formed as illustrated perspective inFig. 3, comprising an arcuate baille wall portion 5| having an arcuatecontour of such a nature that it can be positioned within and generallyconform to the circular contour of the inside face of the tubular sidewall 2| of the impeller. The baille wall 5| is illustrated as beingapproximately 90 in length, approximately the minimum length at which itshould be made to eiect a fair degree of directional contr'ol. Moreaccurately defined directional control can be obtained if the baillewall 5| is made up to 120 or 180 or more in that the direction ofdischarge of the thrown abl rasive may be controlled. As shown in Fig.2, a suitable support for the control cage segment may comprise asupporting plate 55 having a central opening within which a dish-shapedplate 58 is positioned. The plate 58 is provided with an outturnedflange portion 59 secured to the supporting plate 55 as by screws 68.wall 6| 4of the dish-shaped supporting member is provided with a centralopening 62 through which the discharge end 4| of feed spout 40 extends.The control cage segment 50 may be provided with a U-shaped formation 64so designed as to extend around the inturned flange 23 of the tubularimpeller 28. The U-shaped formation 84 presents a ilange portion 64having threaded The bottom The control cage segment 50 positioned withinthe tubular impeller as illustrated effects a measurable degree ofdirectional control of the thrown abrasive. The direction of dischargeof the thrown abrasive may be regulated by shifting the I tip end 54 ofthe control cage segment 50 to the proper clockdial position.

There is shown in Figs. 5 and 6, an abrasive blasting machine whichincludes a bladed rotor and a tubular abrasive impelling device similarto that illustrated in Figs. 1 and 2. In this construction, the abrasivesupply spout 48 is provided with means for scraping the abrasive outthrough the discharge ports 25 in the tubular impeller 20 and anabrasive deecting device 80 which extends into the tubular impeller 20and is adjustably supported in normally stationary position.

The abrasive deilecting device 80, illustrated in perspective in Fig. 7,may be formed from cast metal having a generally arcuate body portion 8|and a trailing end portion 82. A foot portion 85 adjacent the side edgesthereof is provided with threaded openings 18 through which extend thesecuring bolts 63 extending through a selected pair of spaced openings63 in the bottom wall portion 6| of the dish-shaped supporting plate 58.It will be noted that the inner side edge 81 of the deector plate 88 islonger and of greater radius than the outer side edge 88 thereof, sothat when the deector plate is mounted in position Within the tubularimpeller 20 it assumes the position generally illustrated in Figs. 5 and6. The tip end 83 and the trailing end 84 extend generally parallel tothe axis of the rotor. The baille member serves to baille the aircurrents generated Within the rapidly rotating rotor so that theabrasive will be discharged into the path of rotation of the blades b ina direction determined by the clockdial position of the tip end 83 ofthe deilector member.

It will be noted by referring to Fig. 6 that the end portion 19 of thefeed spout extends into the tubular impeller 20 for a substantialdistance and that a spiralling vane 89 is integrally or otherwisefixedly secured to the outer periphery thereof. The spiralling vane 89is shown as comprising three complete turns, each turn increasing indiameter toward the open inner end ofthe spout extension 19. It isappreciated that the vane 89 is normally stationary during rotationofthe bladed rotor. The vane 88 serves to movable collar guide theabrasive discharged into the tubular rotating impeller 28 from the innerend thereof to a position where it may bev discharged through the fullaxial width of the ports 25 of the impeller 28. It will be noted fromFigs. 5.and 6, that the arcuate body portion 8| of the detlector member88 is so positioned that its inner surface is relatively closelyadjacent the periphery of the erable to throw a concentrated stream ofabraspiralling vane 89 and also that the periphery l .eration of themachine by means of a suitable supporting device such as the bracket 42.A re- I85, having an opening |06 through which the feed spout extends,closes the enlarged opening 62 in the dish-shaped supporting member 58.Bolts 83 extending through openings in the collar may be screwed intothreaded apertures in the bottom wall 8| of the dishshaped support toretain the same in position.

In operation, abrasive is supplied to the supply spout 40 and dischargesfrom the end of the end extension 19 into the rapidly rotating tubularimpeller 20 which is fixed to and rotates with the bladed rotor i. Thespiral vane 89 scrapes the abrasive deposited on the inner surface ofthe tubular side wall 2| of the impeller 20 forwardly so that theabrasive is discharged through substantially the full axial width of thedischarge ports 25 therein. The shield member 80 acts to direct theabrasive onto the inner ends of the blades at a predetermined position.

It will be noted by referring to Fig. 5 that the trailing end 84 of thebaille member 80 is positioned close to the interior surface of thetubular wall 2| of the impeller 20, while the tip end 83 thereof ispositioned close to the periphery of the spiral vane 89. The baillemember 80 as illustrated in Figs. 5 and 6 has an arcuate length of 90,which is the shortest length that should be employed to achieve a fairmeasure of directional control. This baiie member 80 may be made up to300 in arcuate length with correspondingly improved directional controlresults. The bale member 88 serves to baiile the air currents so that astream of air at relatively high velocity ows into the tubular impellerthrough the impeller ports 25 during that portion of their path ofrotation which is opposite the baiile and adjacent the trailing end 84thereof, producing through the discharge ports 25 when moving throughthis pressure area. The high velocity air stream and the abrasive escapefrom the tubular impeller outwardly through the ports 25 during thatportion of their path of rotation which is adjacent but in advance ofthe tip end 83 of the deecting member 80, producing what might be termeda suction area. The spiralling vane 89 presents a generally conicalshaped peripheral edge which also cooperates with the arcuate conicalportion 8| of the baille member 80 to effect directional controlresults.

While certain novel features of the invention have been disclosed andare pointed out in the annexed claims, it will be understood thatvarious omissions, substitutions and changes may be made -by thoseskilled in the art without departing from the spirit of the invention.

what is claimed is: 1. A centrifugal abrasive blasting machine opsiveover a predetermined limited arc including in combination, a rotor headmounted for high speed rotation having a plurality oi spaced radiallyextending abrasive throwlngblades supported thereby, the inner ends ofsaid blades extending inwardly short of the axis of rotation of therotor to provide a central space, a tubular impeller positioned withinsaid central space fixed to rotate with said rotor and operative toretain abrasive therein for a suiiicient interval to transmit to theabrasive a centrifugal speed corresponding to the speed of rotation ofthe impeller, said impeller having a plurality of spaced abrasivedischarge ports in the tubular side wall thereof, an abrasive supplyspout for conducting abrasive into saidV tubular impeller, and anormally stationary control device having an arcuate shaped side wallportion extending into said impeller and overlapping a limited arcuatesection o f the tubular side wall of said impeller and covering theports in said section, said control device being operable to direct theabrasive through certain of the uncovered ports of said impeller andinto the path of rotation of the inner ends of said blades during apredetermined limited arc of rotation thereof.

2. A centrifugal abrasive blasting machine operable to throw aconcentrated stream of abrasive over a predetermined limited arcincluding in combination, a rotor head mounted for high speed rotationhaving a plurality of spaced radially extending abrasive throwing bladessup- Iported thereby, the inner ends of said blades extending inwardlyshort of the axis of rotation of the rotor to provide a central space,a.tubular impeller -positioned'within said central space fixed to rotatewith said rotor, said impeller having a plurality of spaced abrasivedischarge ports in the tubular side wall thereof, an abrasive supplyspout for conducting abrasive into said tubular impeller, a normallystationary tubular control cage extending into said central space andenclosing the discharge ports of said impeller, said control cage havinga discharge opening in the tubular side wall of hunted peripheral extentpositioned between the side edges of said blades operable to direct theabrasive into the path of rotation of the inner ends of said bladesduring a -predetermined limited arc of rotation thereof, and means foradjustably supporting said control cage in normally stationary position.

3. A centrifugal abrasive blasting machine operable to throw aconcentrated stream of abrasive over a predetermined limited arcincluding in combination, a rotor head mounted for high4 speed rotationhaving a plurality of spaced radially extending abrasive throwing bladessupported thereby, the inner ends of said blades extending inwardlyshort of the axis of rotation of the rotor to provide a centralspace, atubular impeller positioned within said central space fixed to rotatewith said rotor and operative to retain abrasive therein for sufficientinterval to transmit to the abrasive a centrifugal speed correspondingto the speed of rotation of the impeller, said impeller having aplurality of spaced abrasive discharge ports in the tubular side wallthereof, each of said ports having the side edges thereof positionedbetween the, channel confines of the adjacent blade, said ports beingrelatively short in peripheral extent, a feed spout for conductingabrasive into said tubular impeller, and

a normally stationary control device having an arcaute shaped wallportion extending into said impeller and covering a limited number ofthe -ports in said impeller, said control device being operable vtodirect the abrasive through certain of the uncovered ports in saidimpeller and into the path of rotation of the inner ends of said bladesduring a predetermined limited arc of rotation thereof.

4. A centrifugal abrasive blasting machine operable to throw aconcentrated stream of abrasive over a predetermined limited arcincluding in combination, a rotor head mounted for high speed rotationhaving a plurality of spaced radially extending abrasive throwing bladessupported thereby, the inner ends of said blades extending inwardlyshort of the axis of rotation of the rotor to provide a central space, atubular impeller positioned within said central space fixed to rotatewith said rotor and operative to retain abrasive therein for asufflcient interval to transmit to the abrasive a centrifugal speedcorresponding to the speed of rotation of the impeller, said impellerhaving a .plurality of vspaced abrasive discharge' ports in the tubularside wall thereof, each of said ports having the side edges thereofpositioned between the channel confines of the adjacent blade, saidports being relatively short in peripheral extent, a feed spout forconducting abrasive into said tubular impeller, deecting elements xed tothe interior of said tubular impeller for guiding the abrasive to thedischarge ports thereof, and a normally stationary control device havingan arcuate side wall portion extending into said impeller and covering alimited number of the ports in said impeller, said control device beingoperable to direct the abrasive through certain of the uncovered portsof said impeller and into the path of rotation ofthe inner ends of said-.blades during a predetermined limited arc of rotation thereof.

5. A centrifugal abrasive blasting machine operable to throw aconcentrated stream of abrasive over a predetermined limited arcincluding in combination, a rotor head mounted for high speedrotationjhaving a plurality of spaced radially extending abrasivethrowing blades supported thereby, the inner ends of said bladesextending inwardly short of the axis of rotation of the rotor to providea central space, a tubular impeller positionedl within said centralspace xed to rotate with said rotor and operative to retain abrasivetherein for a suicient interval to transmit to the abrasive acentrifugal speed corresponding to the speed of rotation of theimpeller, said impeller having a plurality of spaced abrasive dischargeports in the tubular side wall thereof equal in number to the number ofblades carried by said rotor, each of said ports having the side edgesthereof positioned between the channel confines of the adjacent blade,said ports being relatively short in peripheral extent and positionedslightly in advance of their corresponding blades, a feed spout forconducting abrasive into said tubular impeller, and an arcuate sha-peddeflector wall extending into said central space and interiorly around alimited arcuate section of the tubular side wall of said impeller andcovering the ports in said section whereby the discharged abrasive willbe directed through certain of the uncovered discharge ports in saidimpeller.

6. A centrifugal abrasive blasting machlne operable to throw aconcentrated stream of abray sive over a predetermined limited arcincluding 1n combination, a rotor head mounted for high speed rotationhaving a plurality of spaced ra-v the rotor to provide a central space,a tubularl impeller positioned within said central space 'fixed torotate with saidirotor, said impeller having a'- plurality of spacedabrasive discharge ports in the tubular side wall thereof, each of saidports having the side edges thereof positioned between 4the channelconfines of the adjacent blade, said ports being relatively short inperipheralextent,

a feed spout for conducting abrasive into said tubular impeller, anarcuate shaped deflector plate extending into said impeller andoverlapping a limited arcuate section of the tubular side wall of saidimpeller and covering the ports in said section whereby the dischargedabrasive will -be directed through certain of the uncovered dischargeports in said impeller, a normally stationary supporting platepositioned exterior to said impeller and having an aperture throughwhich the discharge end of said feed pipe extends, and

means associated with said supporting plate and 1 said deector plate foradjustably securing said deilector plate to said supporting plate.

7. A centrifugal abrasive blasting machine operable to throw aconcentrated stream of abrasive over a predetermined limited arcincluding in combination, va rotor head mounted for high speed rotationhaving a plurality of spaced radially extending abrasive throwing bladessupported thereby, the inner ends of said blades extending inwardlyshort of the axis of rotation of the rotor to provide a central space, atubular impeller positioned Within said central space xed to rotate withsaid rotor and operative to retain abrasive therein for a sulcientinterval to transmit to the abrasive a centrifugal speed correspondingto the speed of rotation of the impeller, said impeller having aplurality of spaced abrasive discharge ports in the tubular side wallthereof equal in number to the number of blades carried by said rotor,said ports being relatively short in peripheral extent and positionedslightly in advance of their corresponding blades, a feed spout forconducting abrasive into said tubular im-peller, and an arcuate shapeddeilector section extending into said impeller and covering a limited-arcuate ported section of the tubular side wall of said impellerwhereby the discharged abrasive will be directed through certain of theuncovered discharge ports in said impeller. 8. A centrifugal abrasiveblasting machine operable to throw a concentrated stream of abrasiveover a predetermined limited arc including in combination, a rotor headmounted for high speed rotation having a plurality of spaced radiallyextending abrasive throwing blades supported thereby, the inner ends ofsaid blades extending inwardly short of the axis of rotation of therotor to provide a central space, a tubular impeller positioned withinsaid central space and having a tubular side wall and a closed rear endwall fixed to said rotor head to rotate therewith and operative toretain abrasive therein for a suiiicient interval to transmit to theabrasive al the tubular side wall thereof, a feed 'spoutr for conductingabrasive into said tubular impeller, an arcuate shaped deilector plateextending into Asupporting plate.

9.'A centrifugal blasting machine operable to throw a concentratedstream of abrasive over a predetermined limited arc including incombination, a rotor head mounted for high speed rotation having aplurality of spaced radially extending abrasive throwing bladessupported thereby, the inner ends of said blades extending inwardlyshort of the axis of rotation of the rotor to provide a central space,an impeller positioned within said central space fixed to rotate withsaid rotor and operative to retain abrasive therein -for a suflilcientinterval to transmit to the abrasive a centrifugal speed correspondingtothe speed of rotation of the impeller, said impeller having a tubularside wall comprising a generally tapered the ports in said section, saidcontrol device being operable to direct the abrasivethrough certain ofthe uncovered discharge ports of said impeller and into the path ofrotation of the inner ends of said blades during a predetermined limitedarc of rotation thereof.

l0. A centrifugal blasting machine operable to throw a concentratedstream of abrasive over a said impeller and into the path of rotation ofthe rotor and operative to retain abrasive therein for a sumcientinterval to transmit to the abrasive a centrifugal speed' correspondingto the speed of rotation of the impeller, said impeller having a tubularside wall comprising a generally tapered side wall portion and agenerally cylindrical side wall portion adjacent the inner ends of saidblades, said cylindrical portion having a plurality of spaced abrasivedis- Charge DOI'S therein. deflecting elements fixedl l to the interiorof said tapered side wall portion for guiding the abrasive to thedischarge ports thereof, and a normally stationary control device havingan arcuate shaped side wall portion extending into said impeller andcovering a limited number of 'the ports in said impeller, said controldevice being operable to direct the abrasive through certainv of theuncovered ports of inner ends of said blades during a predeterminedlimited arc of rotation thereof.

l2. A centrifugal blasting machine operable to throw a concentratedstream of abrasive over a -predetermined limited are including incombination, a rotor head mounted for high speed rotation having aplurality of spaced radially extending abrasive throwing bladessupported thereby, the inner ends of said blades extending predeterminedlimited arc including in combinathe inner ends of said blades extendinginwardly short of the axis of rotation of the; rotor to provide acentral space, an impeller positioned within said central space ilxed torotate with said rotor and operative to retain abrasive therein for asutilcient interval to transmit to the abrasive a centrifugal vspeedcorresponding to the speed of rotation of the impeller, said impellerhaving a tubular side wall comprising a generally tapered side wallportion and a generally cylindrical side wall portion adjacent the innerends of said blades. said cylindrical portion having a plurality ofspaced abrasive discharge ports therein, and an arcuate shaped deiiectorplate extending into said central space and interiorly covering alimited arcuate ported section of the tubular side wall of said impellerwhereby the discharged abrasive will be directed through certain o f theuncovered discharge ports in said im-peller.

1l. A centrifugal blasting machine operable to throw a concentratedstream of abrasive over a predetermined limited arc including incombination, a rotor head mounted for high speed rotation having aplurality of s paced radially extending abrasive throwing bladessupported thereby, the inner ends of said blades extending inwardlyshort of the -axis of rotation of the rotor to provide a central space,an impeller positioned within said central space fixed to rotate withsaid inwardly short of the axis of rotation of the rotor to provide acentral space, a generally tubular shaped impeller having a closed endwall and a tubular side wall positioned within said central space fixedto rotate with said rotor and operative to retain abrasive therein for asumcient interval to transmit to the abrasive a centrifugal speedcorresponding to the speed of rotation of the impeller, said impellerhaving a plurality of spaced abrasive discharge ports in the tubularside wall thereof equal in number to the number of blades carried bysaid rotor, an abrasive supply spout for conducting abrasive into saidtubular impeller, a spiralling rib extending around the innei end ofsaid feed spout for deilecting the abrasive for discharge substantiallythrough the full axial width of said'discharge ports, and a normallystationary control device comprisinga baille plate extending into andcovering a limited number of the ports in said impeller operable todirect the abrasive through certain of the uncovered ports of saidimpeller and into the path of rotation of the inner ends of said bladesduring a `predetermined limited arc of rotation thereof.

13. A centrifugal blasting machine operable to throw a concentratedstream of abrasive over a predetermined limited arc including incombination, a rotor head mounted for high speed rotation having aplurality of spaced radially extending abrasive throwing bladessupported thereby, the inner ends ofsaid blades extending inwardly shortof the axis of rotation of the rotor to provide a central space, agenerally tubular shaped impeller having a closed end wall and a tubularside wall positioned within said central space fixed to rotate with saidrotor and operative to retain abrasive therein for a sumcient intervalto transmit to the abrasive a cen- .trifugal speed corresponding to thespeed of rotation of the impeller, said impeller having a plurality ofspaced abrasive discharge ports in the tubular side wall thereof equalin number to the number of blades carried by said rotor, an abrasivesupply spout for conducting abrasive into said tubular impeller, aspiralling rib extending around the inner end of said feed spout fordefiecting the abrasive Afor discharge sub'- stantially through the fullaxial width of said discharge ports, and an arcuate shaped deflectorplate extending into said central space and interiorly around a limitedarcuate ported section of the tubular side wall .of said impellerwhereby the discharged abrasive will be -directed through certain of theuncovered discharge ports in said 4 impeller.

14. A centrifugal blasting machine operable to throw a concentratedstream of abrasive over a predetermined limited arc including incombination, a rotor head mounted for high speed rotation having aplurality of spaced radially extending abrasive throwing bladessupported thereby, the inner ends of said blades extending inwardlyshort of the axis of'rotation of the rotor to provide a central'space, agenerally tubular shaped impeller having. a closed end Wall and atubular side wall positioned Within said central space fixed to rotatewith said rotor and operative to retain abrasive therein -for asuiiicient interval to transmit to the abrasive a centrifugal speed aspiralling rib having atapering periphery extending around the-inner endof said feed spout for deflecting the abrasive for dischargesubstantially through the full axial width of said discharge ports,and-a control device having an yarcuate shaped deilector sectionextending into directed through certain of the uncovered discharge portsin said impeller.

15. A centrifugal abrasive blasting machine operable to throw aconcentrated stream of abrasive over a predetermined limited arcincluding in combination, a rotor head mounted for high speed rotationhaving a plurality of spaced ra.- dially extending abrasive throwingblades supported thereby, the inner ends of said blades extendinginwardly short of the axis of rotation of the rotor to provide a centralspace, a tubular impeller positioned within said central space andhaving a tubular side wall anda closed rear end wall xed to said rotorhead to'rotate therewith, said impeller having a plurality of spacedabrasive discharge ports. in the tubular side wall thereof, an abrasive.supply spout for conducting abrasive into said tubular impeller, and anormally stationary abrasive control device having an arcuate shapedwall portion extending intosaid impeller and overlapping a limitedarcuate section of the tubular side Wall ofsaid impeller and coveringthe ports in said'` section, said control device having means operableto direct the abrasive through certain of the uncovered p orts 'of saidimpeller and into the path of rotation of mined limited arc of rotationthereof.

CHESTER E. UNGER.

